Causes of failure of insulator
The causes of the failure of insulator are :-
- Cracking of insulator: The main cause of cracking is due the stress produced in the porcelain due to unequal expansion and construction produced in cement, steel and porcelain caused by seasonal heat cold, dryness, and dampness or by heating of the insulator. To avoid such cracking, many improvements in the designs have been made, sometimes cushions are placed in between shells and steel pins in order to allow for its expansion.
- Defective of materials: If the material is defective anywhere, it will puncture from these and thus becomes unfit for further use.
- Porosity of the materials: If the porcelain is manufactured at lower temperatures, it will make it porous, and due to this reason it will absorb moisture from air or from cement and thus becomes unfit for further use.
- Improper glaze: If material is not properly glazed, the water will stick to it which will result into deposition of dust etc. over it which is partially and reduces the flashover distance. Causes the insulators may be damaged.
- Flash over: If there is a flash from one metal part to other, it will cause over-heating and will result into shattering of it.
- Mechanical Stress: The pulling of the insulator may also sometimes cause mechanical stress in it ( if its material is defective ) due to which it may break.
- Short circuit: The large birds may also sometimes cause arc and thus may result in failure of the insulators (it is possible only if the spacing between the conductors is less).
Multiple Choice Question (MCQ) of Materials page-6:51. The permeability and permittivity of a medium are
A) independent of each other
B) related by the atomic number
C) related by the Boltzmann’s constant
D) related by the velocity of electromagnetic waves.
Multiple Choice Question (MCQ) of Materials page-5:41. Bakelite is
A) highly inflammable
B) low resistance conductor
C) a semi-conductor
Multiple Choice Question (MCQ) of Materials page-4:31. Which of the following pairs is commonly used in thermocouples?
D) Silver-German silver.